Electronic Configuration of First 30 Elements

Electronic configuration is defined as the distribution of the electrons of an atom into its orbitals according to the rules. This distribution is fixed for every element. Every element has a definite number of protons which is its atomic number. The number of electrons is the same as the number of protons in an atom. Therefore, we can say that in its neutral state, the atomic number of the element is equal to the number of electrons. The atomic number is the characteristic feature of an atom. The unique distribution of electrons along atomic orbitals is responsible for the element’s specific chemical and physical properties. Therefore, it’s very important to know and study the electronic configuration of all elements.

In order to understand the electronic configuration of elements, it’s important to have a basic understanding of the shells, subshells and orbitals. Filling of the electrons or the distribution of the electrons occurs in the atomic orbitals. Different subshells have a different number of orbitals. And each shell has a different number of subshells. 

This page will help you understand what an electronic configuration is. Also, you will get to know the electronic configuration of the first 30 elements in an ascending order.

Understanding the Electronic Configuration

Every shell has designated a value which is basically the Principal Quantum number, ‘n’. So, for the 1st shell n = 1, for the 2nd shell n = 2, for the 3rd shell n = 3, and so on.

      n   =  1     2    3    4…

  Shell = K    L   M   N…

The number of subshells in a shell is equal to the value of its principal quantum number and each subshell has a value which is called the Azimuthal Quantum number, ‘l’. For instance, for the 1st shell, n=1, so the number of possible subshells is just 1 and the value for ‘l’ is 0. For the 2nd shell, n=2, so the number of subshells is 2 and the values for ‘l’ are 0 and 1. Similarly, it goes further. For every value of ‘l’, we have a corresponding symbol such as:

                               Value of l = 0 1   2   3   4 …

 Symbol/notation for subshell = 

So, the notation for different Subshells goes in this way:

Subshells can have just one orientation or more than one orientation along the coordinate axis in which the electron density can be found and these 3-D spaces around which the probability of finding an electron is maximum is said to be orbital. In simple words, one subshell can be thought to have just one orbital or more than one orbitals for the filling of the electrons. The number of orbitals depends on the value of ‘l’ and each orbital can accommodate a maximum of 2 electrons.

The number of orbitals for a given subshell is equal to 2l + 1. 

So, in the case of 1s (2 * 0 + 1=1, 1 orbital only), the subshell itself acts as orbital. Similarly, for 2s, there’s just one orbital and the subshell itself acts as orbital. For 2p, the possible number of orbitals is 3 (2 * 1 + 1 = 3), which are 2p_x, 2p_y, 2p_z, so the 2p subshell has possible orientations in which electrons can be accommodated, i.e. 2p subshell has 3 orbitals, and so on.

And as stated earlier, each orbital can accommodate a maximum of 2 electrons. So, 1s can accommodate 2 electrons, 2s can accommodate 2 electrons, 2p can accommodate 6 electrons (3 orbitals * 2 electrons each = 6 electrons), and so on.

Also, the filling of the electrons for writing the electronic configuration of the elements is done according to the Aufbau rule, Pauli’s exclusion principle and Hund’s rule.

Aufbau rule states that the order of filling various subshells by means of increasing order of energy levels using the (n + 1) rule. The order of the filling of the orbitals is as follows according to the Aufbau rule/principle:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d, 6p, 7s, …

Exception: Half-filled orbitals are more stable when compared to completely filled orbitals and partially filled orbitals, which can lead to violation of the Aufbau principle.

Now we are ready to write the electronic configurations of the first 30 elements with their atomic numbers.

Table Showing the Electronic Configuration of First 30 Elements 

Cr and Cu act as exceptions. Their electronic configuration has half and fully filled atomic orbitals, i.e. 3d⁵4s¹ and 3d¹⁰4s¹, respectively, which are more stable than partially filled orbitals such as 3d⁴4s² or 3d⁹4d².

The above table showed the 1 to 30 elements electronic configuration along with their respective atomic numbers of elements from 1 to 30. Just like 1 to 30 elements electronic configuration, electronic configuration of all elements can be written accordingly.

Facts on Electronic Configuration

• The electronic configuration of an element is used to determine where the electrons in that element are placed.

• Electrons are ordered in ascending order from the lowest to the greatest energy level.

• The atomic number of an element is largely determined by its electronic configuration.

• The electronic configuration of an atom aids in defining the valency of an element, which in turn aids in predicting its reactivity.

• The electronic configuration can also be used to understand atomic spectra.

• Noble gases, such as Neon, Argon, and Helium, are the most stable because their outermost electrons are completely occupied. The inertness of noble gases is due to their filled valence shells.

• The electronic configuration of both copper and chromium is peculiar in that the 3d- orbitals are filled first, rather than the 4s orbitals.

• Chromium - [[Ar]] 3d⁵4s¹ - The atom's stability is enhanced by the d-orbital, which is filled with single electrons. Copper - [[Ar]] 3d¹⁰4s¹'s d-orbital is similarly completely filled with paired electrons, assuring the atomic structure's stability.